welding arches? does the fuel tank.have to come of!

[Shiz]

right guys genuine question, need the arches welded therefore.to prevent the car going up in flames rcommended that the tank is takin out. however reading up on this it sounds like quite a hassle. has anyone done this before?

[bmw9818]

my mate sorted his arches he left the tank in,

[daimlerman]

Bodywork first on mine,but it was just the outer arch that was repaired.

I would guess that your bodyman is concerned regarding a potential fire hazard,if the tank is that bad it will need changing anyway!

[Grrrmachine]

I did all my inner arch and sill repairs with the tank still in place, but I used some plates of 1mm aluminium to form a heat shield. It won't do anything against stray sparks (which go everywhere!) but it gives some protection against local heat build-up.

[Jos]

Vapour is the problem not heat. Take the bloody tank out, not worth the risk. And then you can inspect all the other rusty bits behind the tank as a bonus.

[Shiz]

Thanks guys for the feedback. But yeah was thinking this, it needs the trailing arm replaced, so that will have to come of anyways. Just wouldnt be to familar with taking the driveshaft & diff out etc. Is there any threads on here that may be helpful. I know its just a case of nuts and bolts. However I mind reading about balancing the driveshaft etc. It sounds like a lot of hassle that could end up in a nightmare. The tank itself looks spot on. Just needs a new vent line.

[daimlerman]

Just needs a new vent line.

I have usually found that just the last inch or so of the tank end perishes and can be trimmed back to get a leak free join.

Driveshafts/diff is not very difficult really,but I would expect that the bushes that support your axle carrier(have a look at my piccie above)will be needing replacement.

Support the car properly at the rear jacking point on the ends of the cills using some packing to protect the seam.

Take the diff out first,leaving the driveshafts attached to the rear beam,then the rear beam will be better balanced to drop down.When I did the job,as you can see in my piccie,I left the diff in place and had a proper struggle to get the lot out in one bit.

Going back,I did it all in bits;
Fuel tank first
Brake lines that pass over the top of the beam
Beam
Diff
trailing arms

That way I found each bit was just about managable on my own!

Always use a decent jack to support the diff,they hurt when they land on your fingers!

[Shiz]

Thanks daimlerman for your response.

The hole vent line itself looks to be rusted. So you would recommend taking the tank out rather than chancing it?

The steps I would go would be as follows correct me if I am wrong.

1:- Jack car up, place on jack stands under the sills.
2:- Take the wheels off.
3:- Unscrew the heat shield, and bolts holding on exhuast.
4:- Remove Exhaust
5:- Then either remove the drive arms.
6:- so whats left is the hubs, traling arms, diff and driveshaft.

My understanding is that there all bolted on, its just a matter of screwing of. But do you have to mark on the driveshaft corresponding to the diff a mark, so that when you are putting it back together it is in the exact same positiong cause its balanced. Is this correct or not. Please feel free to share your thoughts. I dont really want to take things of, then ending up in a handlebars... . Another thing is to, do I have to drain any fluid ? other than petrol tank?.. I would have to drain the brakes to wouldnt I?


Thanks

[daimlerman]

Vent line is a rubber tube running from the top of the tank via the rear o/s arch to a breather tank mounted high in the o/s arch above the filler point.
I think the rusty bit you are refering to is nothing more than a cover for it as it passes through the arch.If this will not clean up and repaint(most will not,TBH!)a replacement can be ordered from your local dealer,takes a couple of days.

Prop/diff does not need to be marked,if you ever need to split the propshaft for any reason,though,you will find two white dots on it to aid re-aliegnment.

Your 'batting order' looks fine.
There should be a drain point in the bottom of the tank,but I have never been able to unfasten one! Pattern tanks do not have one,so if you cannot see a drain point,do not worry.

Brake lines to the rear will have to be split,most doing this kind of extensive strip and build will opt to replace the flexi hoses with braided stainless steel items so sacrificing the flexi where it passes over the rear beam is a good place to cut into.
I would drain the diff,bad enough if you drop the thing on your mitt,but when it then rolls away it will land upside down and wee via it's breather!

You will be suprised at how easily it will all unbolt,BMW used good quality fasteners that seem to respond to a soak in WD40 or similar.Your real difficulty will be the top bolts on the diff,these are 19mm and the top two are only reachable with a flat ring spanner,and you will probably need to link another to it to get enough leverage to 'crack' them.

To get the complete rear suspension,rear beam and fuel tank like in my photo,allow yourself at least half a day.

[Shiz]

I know the very thing your talking about however its not that. Its the line same as the one in this picture, the outer line :-

http://i284.photobucket.com/albums/ll18 ... bmw045.jpg

So taking out the prop/diff is a simply matter of unscrewing and dropping out ?.. I wouldnt need to split the propshaft during this process no ?...

So there is no way of unscrewing the brake lines?.. I have seen those SS braided flexi lines before. When you say rear beam, do you mean the rear axle part ?. Sorry if my terminology is wrong. With reading through this, you have reassured me a little, it seems to mainly take my time, and hopefully have playful bolts to play with lol.

Did you drop the rear axle, trailing arms, drive arms, hubs and diff all at the once ?.. It looks like that in your pic.

Thanks again buddy for your feedback

[daimlerman]

That outer line in your photo(put [IMG] at each end!) is the breather line that terminates at a carbon filter in the engine bay,if fitted,or is tucked into the n/s suspension turret.Available is steel from the dealer to order or could be replaced with kunifer,I guess.

You can certainly have a go at unscrewing the brake lines,but TBO,the one's that pass over the rear beam(or axle carrier,or rear axle part) are such a swine to get at that I would replace whilst you are in there.Ordinary rubber one's from your local factor will do,no need to fit stainless one's,but the stainless will last a lot longer!

Yes,I dropped the lot in one bit,BUT,if doing it again I would do it in bits,as it's very difficult to find a balance point that allows the beam to drop off it's mounts square.These beam mounts do seem to glue themselves to the car's shell and can be very 'playful' to get free.

Please do not worry about asking questions,if I,or any other zoner can help you we will try to